1. Field of the Invention
The invention relates to an evaporated fuel adsorbing apparatus for an internal combustion engine.
2. Description of the Related Art
In an internal combustion engine, fuel in cylinders may be evaporated and diffused in an intake passage after the engine stops. Thus, for example, Japanese Patent Application Publication No. 2002-39025 (JP-A-2002-39025) describes a technology in which a concave portion is formed in the inner wall of a surge tank that constitutes the intake passage of an internal combustion engine, and a fuel adsorbing member that adsorbs fuel is provided in the concave portion. With this configuration, the fuel adsorbing member adsorbs the evaporated fuel that remains in the intake passage. Therefore, it is possible to reduce the concentration of fuel in the intake passage.
In some internal combustion engines, a blow-by passage may be connected to the portion of the intake passage upstream of a throttle valve. Blow-by gas in a crankcase is introduced into the intake passage through the blow-by passage. Because the blow-by gas contains evaporated fuel and oil mist, the oil mist flows into the intake passage through the blow-by passage. Thus, in the technology described in Japanese Patent Application Publication No. 2002-39025, the fuel adsorbing member may adsorb the oil mist, and accordingly, the fuel adsorbing member may deteriorate,
Japanese Patent Application Publication No. 2003-214263 (JP-A-2003-214263) describes a technology in which a fuel adsorbing member is provided in a resonator that is provided upstream of a throttle valve in an intake passage. With this configuration, because the fuel adsorbing member is provided in the resonator, the fuel adsorbing member is unlikely to contact the oil mist in the intake passage. However, with this configuration, because the fuel adsorbing member is provided upstream of the throttle valve in the intake passage, that is, the fuel adsorbing member is provided at a position far from the cylinders, it is not possible to suppress an increase in the concentration of fuel in the intake passage at a position near the cylinders, i.e., an increase in the concentration of fuel in an intake manifold or a surge tank. Therefore, when flame is generated during a combustion stroke, and the flame is not extinguished and remains until a next intake stroke, for example, at the time of cold start, it is not possible to sufficiently suppress the phenomenon that the flame in the cylinder flows back to the intake passage through an intake port, i.e., so-called back fire. This back fire may decrease the durability of an intake pipe.